package org.apache.lucene.queryParser;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.MultiPhraseQuery;
import org.apache.lucene.search.PhraseQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.Version;

/**
 * A QueryParser which constructs queries to search multiple fields.
 *
 * @version $Revision: 965592 $
 */
public class MultiFieldQueryParser extends QueryParser {
    protected String[] fields;
    protected Map<String, Float> boosts;

    /**
     * Creates a MultiFieldQueryParser. 
     * Allows passing of a map with term to Boost, and the boost to apply to each term.
     *
     * <p>It will, when parse(String query)
     * is called, construct a query like this (assuming the query consists of
     * two terms and you specify the two fields <code>title</code> and <code>body</code>):</p>
     * 
     * <code>
     * (title:term1 body:term1) (title:term2 body:term2)
     * </code>
     *
     * <p>When setDefaultOperator(AND_OPERATOR) is set, the result will be:</p>
     *  
     * <code>
     * +(title:term1 body:term1) +(title:term2 body:term2)
     * </code>
     * 
     * <p>When you pass a boost (title=>5 body=>10) you can get </p>
     * 
     * <code>
     * +(title:term1^5.0 body:term1^10.0) +(title:term2^5.0 body:term2^10.0)
     * </code>
     *
     * <p>In other words, all the query's terms must appear, but it doesn't matter in
     * what fields they appear.</p>
     */
    public MultiFieldQueryParser(Version matchVersion, String[] fields, Analyzer analyzer, Map<String, Float> boosts) {
        this(matchVersion, fields, analyzer);
        this.boosts = boosts;
    }

    /**
     * Creates a MultiFieldQueryParser.
     *
     * <p>It will, when parse(String query)
     * is called, construct a query like this (assuming the query consists of
     * two terms and you specify the two fields <code>title</code> and <code>body</code>):</p>
     * 
     * <code>
     * (title:term1 body:term1) (title:term2 body:term2)
     * </code>
     *
     * <p>When setDefaultOperator(AND_OPERATOR) is set, the result will be:</p>
     *  
     * <code>
     * +(title:term1 body:term1) +(title:term2 body:term2)
     * </code>
     * 
     * <p>In other words, all the query's terms must appear, but it doesn't matter in
     * what fields they appear.</p>
     */
    public MultiFieldQueryParser(Version matchVersion, String[] fields, Analyzer analyzer) {
        super(matchVersion, null, analyzer);
        this.fields = fields;
    }

    @Override
    protected Query getFieldQuery(String field, String queryText, int slop) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                Query q = super.getFieldQuery(fields[i], queryText, true);
                if (q != null) {
                    //If the user passes a map of boosts
                    if (boosts != null) {
                        //Get the boost from the map and apply them
                        Float boost = boosts.get(fields[i]);
                        if (boost != null) {
                            q.setBoost(boost.floatValue());
                        }
                    }
                    applySlop(q, slop);
                    clauses.add(new BooleanClause(q, BooleanClause.Occur.SHOULD));
                }
            }
            if (clauses.size() == 0) // happens for stopwords
                return null;
            return getBooleanQuery(clauses, true);
        }
        Query q = super.getFieldQuery(field, queryText, true);
        applySlop(q, slop);
        return q;
    }

    private void applySlop(Query q, int slop) {
        if (q instanceof PhraseQuery) {
            ((PhraseQuery) q).setSlop(slop);
        } else if (q instanceof MultiPhraseQuery) {
            ((MultiPhraseQuery) q).setSlop(slop);
        }
    }

    @Override
    protected Query getFieldQuery(String field, String queryText, boolean quoted) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                Query q = super.getFieldQuery(fields[i], queryText, quoted);
                if (q != null) {
                    //If the user passes a map of boosts
                    if (boosts != null) {
                        //Get the boost from the map and apply them
                        Float boost = boosts.get(fields[i]);
                        if (boost != null) {
                            q.setBoost(boost.floatValue());
                        }
                    }
                    clauses.add(new BooleanClause(q, BooleanClause.Occur.SHOULD));
                }
            }
            if (clauses.size() == 0) // happens for stopwords
                return null;
            return getBooleanQuery(clauses, true);
        }
        Query q = super.getFieldQuery(field, queryText, quoted);
        return q;
    }

    @Override
    protected Query getFuzzyQuery(String field, String termStr, float minSimilarity) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                clauses.add(new BooleanClause(getFuzzyQuery(fields[i], termStr, minSimilarity), BooleanClause.Occur.SHOULD));
            }
            return getBooleanQuery(clauses, true);
        }
        return super.getFuzzyQuery(field, termStr, minSimilarity);
    }

    @Override
    protected Query getPrefixQuery(String field, String termStr) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                clauses.add(new BooleanClause(getPrefixQuery(fields[i], termStr), BooleanClause.Occur.SHOULD));
            }
            return getBooleanQuery(clauses, true);
        }
        return super.getPrefixQuery(field, termStr);
    }

    @Override
    protected Query getWildcardQuery(String field, String termStr) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                clauses.add(new BooleanClause(getWildcardQuery(fields[i], termStr), BooleanClause.Occur.SHOULD));
            }
            return getBooleanQuery(clauses, true);
        }
        return super.getWildcardQuery(field, termStr);
    }

    @Override
    protected Query getRangeQuery(String field, String part1, String part2, boolean inclusive) throws ParseException {
        if (field == null) {
            List<BooleanClause> clauses = new ArrayList<BooleanClause>();
            for (int i = 0; i < fields.length; i++) {
                clauses.add(new BooleanClause(getRangeQuery(fields[i], part1, part2, inclusive), BooleanClause.Occur.SHOULD));
            }
            return getBooleanQuery(clauses, true);
        }
        return super.getRangeQuery(field, part1, part2, inclusive);
    }

    /**
     * Parses a query which searches on the fields specified.
     * <p>
     * If x fields are specified, this effectively constructs:
     * <pre>
     * <code>
     * (field1:query1) (field2:query2) (field3:query3)...(fieldx:queryx)
     * </code>
     * </pre>
     * @param matchVersion Lucene version to match; this is passed through to QueryParser.
     * @param queries Queries strings to parse
     * @param fields Fields to search on
     * @param analyzer Analyzer to use
     * @throws ParseException if query parsing fails
     * @throws IllegalArgumentException if the length of the queries array differs
     *  from the length of the fields array
     */
    public static Query parse(Version matchVersion, String[] queries, String[] fields, Analyzer analyzer) throws ParseException {
        if (queries.length != fields.length)
            throw new IllegalArgumentException("queries.length != fields.length");
        BooleanQuery bQuery = new BooleanQuery();
        for (int i = 0; i < fields.length; i++) {
            QueryParser qp = new QueryParser(matchVersion, fields[i], analyzer);
            Query q = qp.parse(queries[i]);
            if (q != null && // q never null, just being defensive
                            (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
                bQuery.add(q, BooleanClause.Occur.SHOULD);
            }
        }
        return bQuery;
    }

    /**
     * Parses a query, searching on the fields specified.
     * Use this if you need to specify certain fields as required,
     * and others as prohibited.
     * <p><pre>
     * Usage:
     * <code>
     * String[] fields = {"filename", "contents", "description"};
     * BooleanClause.Occur[] flags = {BooleanClause.Occur.SHOULD,
     *                BooleanClause.Occur.MUST,
     *                BooleanClause.Occur.MUST_NOT};
     * MultiFieldQueryParser.parse("query", fields, flags, analyzer);
     * </code>
     * </pre>
     *<p>
     * The code above would construct a query:
     * <pre>
     * <code>
     * (filename:query) +(contents:query) -(description:query)
     * </code>
     * </pre>
     *
     * @param matchVersion Lucene version to match; this is passed through to QueryParser.
     * @param query Query string to parse
     * @param fields Fields to search on
     * @param flags Flags describing the fields
     * @param analyzer Analyzer to use
     * @throws ParseException if query parsing fails
     * @throws IllegalArgumentException if the length of the fields array differs
     *  from the length of the flags array
     */
    public static Query parse(Version matchVersion, String query, String[] fields, BooleanClause.Occur[] flags, Analyzer analyzer) throws ParseException {
        if (fields.length != flags.length)
            throw new IllegalArgumentException("fields.length != flags.length");
        BooleanQuery bQuery = new BooleanQuery();
        for (int i = 0; i < fields.length; i++) {
            QueryParser qp = new QueryParser(matchVersion, fields[i], analyzer);
            Query q = qp.parse(query);
            if (q != null && // q never null, just being defensive 
                            (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
                bQuery.add(q, flags[i]);
            }
        }
        return bQuery;
    }

    /**
     * Parses a query, searching on the fields specified.
     * Use this if you need to specify certain fields as required,
     * and others as prohibited.
     * <p><pre>
     * Usage:
     * <code>
     * String[] query = {"query1", "query2", "query3"};
     * String[] fields = {"filename", "contents", "description"};
     * BooleanClause.Occur[] flags = {BooleanClause.Occur.SHOULD,
     *                BooleanClause.Occur.MUST,
     *                BooleanClause.Occur.MUST_NOT};
     * MultiFieldQueryParser.parse(query, fields, flags, analyzer);
     * </code>
     * </pre>
     *<p>
     * The code above would construct a query:
     * <pre>
     * <code>
     * (filename:query1) +(contents:query2) -(description:query3)
     * </code>
     * </pre>
     *
     * @param matchVersion Lucene version to match; this is passed through to QueryParser.
     * @param queries Queries string to parse
     * @param fields Fields to search on
     * @param flags Flags describing the fields
     * @param analyzer Analyzer to use
     * @throws ParseException if query parsing fails
     * @throws IllegalArgumentException if the length of the queries, fields,
     *  and flags array differ
     */
    public static Query parse(Version matchVersion, String[] queries, String[] fields, BooleanClause.Occur[] flags, Analyzer analyzer) throws ParseException {
        if (!(queries.length == fields.length && queries.length == flags.length))
            throw new IllegalArgumentException("queries, fields, and flags array have have different length");
        BooleanQuery bQuery = new BooleanQuery();
        for (int i = 0; i < fields.length; i++) {
            QueryParser qp = new QueryParser(matchVersion, fields[i], analyzer);
            Query q = qp.parse(queries[i]);
            if (q != null && // q never null, just being defensive
                            (!(q instanceof BooleanQuery) || ((BooleanQuery) q).getClauses().length > 0)) {
                bQuery.add(q, flags[i]);
            }
        }
        return bQuery;
    }

}
